U.S. patent number 3,805,731 [Application Number 05/250,531] was granted by the patent office on 1974-04-23 for dual pump waterjet.
This patent grant is currently assigned to North American Rockwell Corporation. Invention is credited to Raymond B. Furst, William J. Mabe, Jr., Kurt Rothe.
United States Patent |
3,805,731 |
Furst , et al. |
April 23, 1974 |
DUAL PUMP WATERJET
Abstract
Two concentrically positioned axial flow pumps are axially
aligned on a single shaft. A high flow pump is positioned outwardly
of an inner high pressure pump, each of the pumps having
independent inlet means. The pumps provide waterjet thrust
efficiently at both low watercraft speeds and high watercraft
speeds by providing dual waterjet inlet ports, and manipulating the
inlet ports to suit the vehicle needs. During low speed, high drag
conditions, both pumps receive water through the dual inlet
openings, and during high speed, low drag conditions, the first
outer high flow pump is shut down by closing off its inlet port,
the remaining high pressure pump providing thrust to propel the
already accelerated watercraft.
Inventors: |
Furst; Raymond B. (Northridge,
CA), Rothe; Kurt (Pacific Palisades, CA), Mabe, Jr.;
William J. (Canoga Park, CA) |
Assignee: |
North American Rockwell
Corporation (El Segundo, CA)
|
Family
ID: |
22948133 |
Appl.
No.: |
05/250,531 |
Filed: |
May 5, 1972 |
Current U.S.
Class: |
440/47;
416/193R |
Current CPC
Class: |
B63H
11/08 (20130101) |
Current International
Class: |
B63H
11/00 (20060101); B63H 11/08 (20060101); B63h
011/08 () |
Field of
Search: |
;115/11,12,14,15,16
;114/150,151 ;60/221,222 ;239/506,507,512 ;416/193,186
;415/77,78,79,155,182 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buchler; Milton
Assistant Examiner: Frankfort; Charles E.
Attorney, Agent or Firm: Humphries; L. Lee Upton; Robert
G.
Claims
We claim:
1. A dual pump waterjet for watercraft comprising:
a first pump means positioned within a first conduit means,
first water inlet means connected to said first conduit means to
direct water into said first pump means,
a first nozzle means at the end of said first conduit means to
direct water out of said first pump means,
a second pump means concentric with said first pump means connected
to and aligned on a common shaft positioned within a second conduit
means concentric with said first conduit means, said first and
second pump means being in flow communication with said first and
second conduit means,
a second water inlet means to direct water into said second pump
means,
a second nozzle means concentric with said first nozzle means
connected to said second conduit means to direct water out of said
second pump means,
a single source of power in driving connection with both said first
and second concentric pump means, and
means to close off one of said inlet means, thereby cutting off
said water to one of said pump means after said watercraft has
accelerated beyond a low speed high drag region.
2. The invention as set forth in claim 1 wherein said dual pump
waterjet is positioned internally within said watercraft, and
wherein said first and second nozzle means are concentric one
within the other, said concentric nozzle means protruding through a
transom of said watercraft to direct water from said dual pumps.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
Waterjet propulsion whereby a stream of water is hydraulically
pumped outwardly from a nozzle driven by a high flowrate pump is
becoming increasingly more popular with watercraft manufacturers.
Usually a water inlet port is located upstream of the pump, the
inlet port being positioned beneath the water line, thus the water
is picked up through the inlet port and directed towards the pump
in the inlet duct. The water is then accelerated by the pump out
the exhaust outlet port or nozzle thus propelling the watercraft
through the water.
2. Description of the Prior Art
There are several examples of hydraulic jet propulsion devices in
the prior art. For example, U.S. Pat. No. 1,548,936 describes a
means for propelling boats, which includes a steam engine to drive
at least a pair of pumps, the pumps being interconnected between an
inlet pipe positioned below the water line which draws in water to
the pump, the pump accelerates the water to exiting outlet pipes
which, in turn, drive the boat forwardly. Additional piping
provides a reverse path for the exiting water which causes the ship
to reverse direction.
Another waterjet propulsion device is described in U.S. Pat. No.
3,007,305. This patent discloses a constant speed, two-stage axial
flow pump inside of an inlet duct being externally driven by an
engine. The inlet duct leading to the two-stage flow pump directs
water into the pump and out through an outlet exhaust nozzle to
propel the vehicle forwardly. Thus both stages "see" the same water
inlet flow.
Another U.S. Pat. No. 3,328,061, similar to the one just discussed,
discloses a pump inside of a water duct, the two-stage device
having a first impeller that is driven at a slower speed than the
second downstream impeller, thus providing varying speed, two-stage
propulsion. The pump draws water through an inlet opening and
outwardly through an exhaust nozzle to propel the craft through the
water. The two-stage device, thus, results in a high speed pumping
unit with corresponding high pressure rise through the unit. A
second U.S. Pat. No. 3,405,526 is issued to the same inventor
(Aschauer), and discloses a similar means to propel water through a
water duct. This patent describes a more sophisticated means to
prevent cavitation between stages, thus effecting a more efficient
pumping operation.
All of the aforementioned patents exhibit the same inefficiencies
relative to thrust versus drag at various watercraft speeds. A
conventional waterjet pump is designed to produce the thrust
required to overcome the boat drag at the maximum boat design
speed. However, at lower speeds, due to reduced pump power or
increased boat loads, the propulsive efficiency is reduced. All of
the aforementioned prior art devices are provided with a single
water inlet port for the driving pump. Therefore, the pump is less
efficient at low speeds and high drag conditions, the pump being
designed to reach its maximum efficiency at a certain watercraft
velocity drag ratio. Therefore, it follows that the pumps are
highly inefficient during low speed, high drag conditions.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide dual pumps
on a single shaft having separate inlet ports for each pump.
More specifically, it is an object of this invention to provide
concentrically oriented pumps on a single shaft, the outer pump
being a high flow pump and the inner pump being a high pressure
pump. Each of the pumps have separate inlet ports, one of the inlet
ports being closed during high speed operation.
The dual pump waterjet may operate with one or two pumps providing
thrust. When two pumps are in operation, the driving engine speed
reduces at constant horsepower for a given engine throttle setting.
The additional pump results in a higher total flowrate which, with
the lower pressure rise, matches the engine power characteristics
at a lower speed. Thus the lower pump pressure rise results in a
lower jet velocity which gives peak propulsive efficiency at a
lesser boat velocity. Hence, more thrust is provided during low
speed, high drag watercraft conditions. The combination of
increased flowrate with a lower jet velocity increases static and
low speed jet thrust. As the watercraft speed increases with both
pumps in operation on a single shaft, the boat characteristic
changes as the velocity increases. As the drag is overcome by the
dual pump operation, the high flow pump is shut down by way of
closing the water inlet duct feeding the high flow pump. Since both
of the pumps are on a single shaft, the high flow pump surrounding
the internal high pressure pump then offers no resistance since it
is no longer in contact with the inlet water flow from its separate
inlet duct. The dual pump waterjet then provides increased thrust
capability in the high drag, low speed region and permits higher
speeds under reduced power settings. Once the high drag region is
overcome, full power is available to drive the single high pressure
pump to provide a high velocity waterjet which is more efficient in
high craft speed regions. Conventional waterjet craft having single
or dual pumps with a single inlet require additional horsepower to
accelerate the watercraft beyond the high drag, low speed region
because of the inefficiency of the single inlet, single pump
operation.
An advantage over the prior art is evident in that the dual pump,
with both inlet ports for each pump open, provides high flow with
lower jet velocity which increases static and low speed thrust
capability during high drag, low speed watercraft conditions. When
the high flow inlet port leading to the high flow pump is closed,
the high pressure pump takes over during high speed operations to
maintain the craft in the high speed, low drag range. In this
region, the inlet drag is reduced by closing the high flow
inlet.
Another advantage over the prior art is realized in that, with the
dual pump operation having separate inlet ports, a lesser
horsepower engine is thus required due to the increased efficiency
of the thrust capabilities of the pumps.
Still another advantage over the prior art is the ability to
accelerate a watercraft in rough water conditions whereby the drag
to velocity ratio is much higher. The advantage lies in the
increased efficiency of the dual inlet, dual pump waterjet, whereby
the increased flowrate of the two pumps in operation is superior to
the single inlet, single pump operation of conventional waterjet
units in rough water.
The above noted objects and advantages of the present invention
will be more fully understood upon a study of the following
detailed description in conjunction with the detailed drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a portion of a watercraft with
a dual pump, dual inlet waterjet device positioned therein;
FIG. 2 is a cross-sectional view of another embodiment illustrating
a portion of a watercraft wherein the propulsion unit is mounted
externally of the craft;
FIG. 3 is a view taken along lines 3--3 of FIG. 2 showing the dual
inlet configuration;
FIG. 4 is a chart illustrating propulsive efficiency percent during
one pump and two pump maximum power settings for a hydrofoil
boat;
FIG. 5 is a chart illustrating thrust or drag pounds versus
hydrofoil craft speed feet per second at various power settings;
and
FIG. 6 is a chart illustrating thrust or drag pounds versus
conventional chart speed feet per second at various power settings
during one pump and dual pump operations.
Referring now to FIG. 1, the waterjet pump generally designated as
10 is mounted within a watercraft 11 normally adjacent the stern or
transom 15. The waterjet pump comprises a pump housing 12 having a
dual nozzle housing 13 attached thereto. Upstream of the dual
nozzle housing 13 is an inlet ducting housing 14 which terminates
in a pair of inlet openings flush with the bottom of the watercraft
11. The inlet ducting 14 comprises a highflow inlet duct 16 which
directs water towards an inlet torus or manifold 17 which
subsequently directs water into the pump generally designated as
35. A separate high pressure inlet duct directs water through
opening 19 into the high pressure pump generally designated as 33.
The water being directed to torus 17 is influenced by flow
straightener 26 immediately before it impacts the high flow
impeller blades 38. Similarly the high pressure water flow entering
inlet 19 of high pressure duct 18 is influenced by a flow
straightener 24 immediately before it impacts the high pressure
pump impeller blades 36.
The power shaft 28 is mechanically connected to a source of power
(not shown) through coupling 30. Bearings 32 support the end of a
drive shaft 34 which leads into the interior of the high pressure
inlet duct 18. The drive shaft 34 terminats in a drive shaft
support housing 40 which contains a set of bearings 42. Immediately
upstream of support housing 40 is a first high pressure pump 33
rigidly affixed to shaft 34. A shroud 37 connected to the outer
tips of the impeller blades 36 separates the high pressure pump 33
from the high flow pump 35 attached to the outer surface of shroud
37. The concentric pumps 33 and 35 thus provide two seprate means
of propulsion. The drive shaft support housing 40 is rigidly
affixed by a multiplicity of support webs and flow straighteners 41
which effect the accelerated flow of water from the plurality of
pitched impeller blades 36 and 38. The support webs 41 serve to
position the outer high flow nozzle 46 with respect to the inner
high pressure nozzle 44 so as to maintain the pair of nozzles
concentrically one within the other.
A mechanically actuatable door 22 is affixed to the bottom of the
hull 11 and is adapted to be moved into and out of engagement with
opening 20 which leads into the high water flow torus 17 and
directs the water through the high flow pump 35. It can readily be
seen then that when the door 22 is moved into blocking position in
opening 20, the water entering duct 16 is arrested thus enabling
the high flow impeller blades 38 to free-wheel within the high flow
passages 16. When this occurs, the high pressure pump 33 is
accelerated with a given power setting, thus causing an increased
pressure rise within the high pressure pump 33, thereby
accelerating the water out of nozzle 44.
The means by which the door 22 is moved into and out of engagement
with opening 20 may be an arrangement of Venetian blinds or slats
as seen in FIG. 3 or the other may be hydraulically actuated into
and out of engagement with opening 20 or hydrodynamic forces may be
utilized to induce the door 22 into and out of engagement with the
opening based on the speed of the watercraft through the water. The
trap door 22 may be closed manually or, alternatively, hydraulic
actuation using the pressure from the pumps may be utilized to
actuate the door.
Turning now to FIG. 2, another embodiment illustrates the waterjet
pump 10 mounted externally of the watercraft on a transom 15. For
example, the dual pumps may be connected to an outboard engine (not
shown). The pump housing 80 has a pair of rearwardly directed
outlet nozzles 82 and 84 connected thereto. Adjacent the bottom of
housing 80 is a high flow inlet duct 86 leading into a high flow
inlet torus 88 in housing 80 that is in flow communication with the
high flow nozzle 82. At the bottom end of inlet 86 is an inlet
opening 90. A second inlet 92 leads into torus 94 in housing 80
which is in flow communication with the high pressure nozzle 84.
Inlet 92 has an independent opening 96 positioned within opening 90
to direct water into the high pressure pump.
A pair of concentric pumps 98 and 100 are fixed to a drive shaft
102. The drive shaft is supported within housing 80 by bearing 104,
the bearing having a seal 106 adjacent thereto. The end of the
drive shaft 102 supports a plurality of pitched high pressure
impeller blades 108. At the end of blades 108 is a fixed annular
shroud 110 that supports a plurality of pitched high flow impeller
blades 112.
The opening 90 may have a series of actuatable slats 114, as viewed
in FIG. 3. The slats are actuatably closed by rotating control rod
116 mechanically linked to each of the slats 114, thus closing off
opening 90 leading through pump 98, thereby shutting down the high
flow pumping operation as heretofore described. A pair of skegs 118
serve to prevent the entering water in openings 90 and 96 from
spilling away from the openings during single or dual pump
operations.
FIG. 4 is a chart indicating propulsion efficiency at both one-pump
maximum power operation and two-pump maximum power operation. Curve
39 indicates a two-pump operation and clearly shows the increased
thrust available at the low watercraft speed range while curve 43
indicates a one-pump maximum power operation with the trap door or
slats closing off the high flow water to the high flow pump, thus
indicating the thrust available at higher watercraft speeds. It can
be seen that the one-pump maximum power operation is more efficient
at the high speed ranges while it is much less efficient at the low
speed, high drag region, as indicated by the curve. Therefore, to
gain maximum efficiency of the watercraft power available, the
two-pump operation indicated by curve 39 is used in the high drag,
low speed ranges to provide maximum thrust up to a certain
watercraft speed, whereupon the inlet to the high flow pump is
closed, thus enabling the one-pump operation to take over, thereby
providing increased speeds at the low drag speed range indicated by
the longer curve 43.
Turning to FIG. 5, a 32-foot hydrofoil boat is used as an example
which has a 344 maximum horsepower engine installed therein. The
chart indicates the performance of the hydrofoil boat at certain
drag conditions at specific speeds. The boat operates during the
high-drag region A (curves 52 and 56) with the boat hull supporting
the weight by buoyancy. Region B is a transition region during
which time the hydrofoils provide a substantial lift. In region C
the hull is lifted free of the water by the hydrfoil lift devices.
The boat drag is increased as the height of the waves in the water
are increased (indicated as curves 52 and 56). At maximum engine
power (344 horsepower) single pump operation provides maximum boat
speed capability at both zero and maximum wave height drag.
However, with a power setting of 170 horsepower (bold curves 48 and
49) or a similar engine of 170 maximum horsepower, the single pump
will marginally overcome the high hump drag point 50 (intersection
of curves 48 and 52) in region B for zero wave height depicted by
curve 52 but will not overcome the drag 54 at maximum wave height
depicted by curve 56. With one pump in operation at 170 horsepower
maximum boat speed capability is 62 ft/sec (intersection 58 of
curves 49 and 52) at zero wave height (curve 52) and 22 ft/sec
(intersection 60 of curves 49 and 56 at maximum wave height (curve
56). With two pumps in operation the thrust is adequate to insure
overcoming phase B maximum drag at both zero and maximum wave
heights. At zero wave height, the maximum speed is 44 ft/sec
(intersection 62 of curves 48 and 52) and at maximum wave height
the maximum craft speed is 33 ft/sec (intersection 64 of curves 48
and 56). Thus it can be seen that the dual pump waterjet provides
increased thrust capability in the high drag low-speed region
(region B) and may permit higher speeds under reduced power under
heavy sea conditions, as shown by the 94 horsepower curves. The
dual pump may also be used to permit use of lower installed power
than for a single waterjet for reduced installation costs. Dual
pump operation also provides high zero and low speed thrust for
freeing boats from sandbars, towing, and the like.
FIG. 6 is a chart which uses as an example a 32 foot conventional
hull boat having a dual pump waterjet installed therein. In this
chart, as in the last chart, the maximum engine power is 344
horsepower and a 94 horsepower throttle setting is indicated by the
curves and dotted line. Thrust values are presented for single and
dual pump operation. Three boat drag levels are presented by curves
66, 68 and 70. Such drag curves occur when workboats operate with
widely varying loads. Dual pump operation permits superior speed
(33 ft/sec) which is indicated by the intersection 72 of curves 74
and 66 at maximum drag compared with (25 ft/sec) that is indicated
by the intersection 78 of curves 76 and 66, when utilizing a single
pump at the same power setting. Single pump operation (curve 76)
permits higher speed at the lower drag level as heretofore
described. The higher speed may be achieved with the dual pump at
the lower drag levels by closing the inlet to the high flow pump
which is specifically designed for the lower speed high-drag
operations. At reduced power levels (94 horsepower) and speeds,
dual pump operation provides maximum boat speed at all drag
levels.
Obviously, other configurations may be utilized, for example, two
separate pumps being driven by a single power output having dual
shafts, the one pump being designed for low speed high drag
conditions while the other pump being designed for high speed high
pressure conditions, the two pumps being operated so as to
shut-down the high flow pump after the high drag region is
overcome, thus allowing the high pressure pump to take over.
* * * * *